نوع مقاله : مقاله کامل علمی- پژوهشی
نویسندگان
1 مؤسسه تحقیقات برنج کشور معاونت مازندران آمل-ایران
2 دانشیار گروه زراعت، دانشگاه علوم کشاورزی ساری
3 استادیار پژوهش، مؤسسه تحقیقات برنج کشور معاونت مازندران،آمل
4 استادیار پژوهش، پژوهشکده ژنتیک و زیست‌فناوری کشاورزی طبرستان، ساری
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives:
Nitrogen (N) and radiation are important and effective factors on nitrogen uptake and rice yield. Dimming is a new phenomenon in climate change process, and few studies have been conducted on its effects on rice. Therefore, this study aimed to evaluate the effects of reduced radiation at different growth stages on paddy yield (PY) and nitrogen use efficiency (NUE) under varying N application rates.
Materials and methods:
The experiment was conducted in 2018 using a split-split plot arrangement based on a randomized complete block design with three replications. The study focused on the Shiroudi, a high-yielding cultivar commonly grown in Mazandaran Province, Iran. The treatments included four different levels of N (0, 46, 92, 138 kg/ha) and three radiation levels (natural light, 30% shading, and 60% shading) applied during three stages of vegetative, reproductive, and grain filling stages using standard shade nets. At harvest stage, PY, N absorption in straw and grain, and NUE indices were measured using specific equations.
Results:
The results indicated that with the reduction of N consumption efficiency, particularly recovery efficiency (REN) and N internal efficiency (IEN) decreased by up to 80% at the highest N application rate 138 kg of N fertilizer. In contrast, the amount of N harvest index (NHI), partial factor productivity (PFPN), agronomic efficiency (AEN) and physiological efficiency of N (PEN) increased up to 46 kg/ha under the conditions of reduced radiation condition but declined sharply thereafter. According to the findings, the highest PY was achieved with 9167 kg/ha in the treatment of 92 kg of N and natural light, whereas the lowest PY was observed with 4593 kg/ha in the treatment with no N and 60% shading during the reproductive and grain filling stage. protein content ranged from 11.7% in the treatment with 138 kg of N fertilizer and 60% shading during the grain filling stage to 5.57% in the control treatment (no N under natural light).
Conclusion:
According to the results of this research, the increased N application under reduced radiation conditions leads to a decline in N efficiency indicators and PY. In the conditions of reduced radiation, increasing the application of N from 46 to 92 kg per hectare resulted a reduction in agronomic efficiency and physiological efficiency by about 40%. Although based on the findings, optimal N application rate for Shiroudi variety under conditions of the research area was determined to be 92 kg/ha, but under shading conditions, the treatment of 46 kg/ha of N performed better than the 92 kg treatment. Therefore, optimizing N application based on solar radiation levels can reduced environmental pollution, lower production costs and enhance of PY.
کلیدواژه‌ها [English]
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